During fiscal year of 2009, we used ChIP-chip and gene expression microarray approaches to examine the role of p53 in embryonic stem cells. We surprisingly found that p53 regulates the Wnt sginaling pathway in embryonic stem cells. The Wnt signaling pathway plays important role in development and tumorigenesis. The underlying mechanism is currently under investigation in the lab. In the future, we plan to use in vivo mouse model to test our hypothesis that p53 has dual functions in embryonic stem cells.